Dietary fibre and the gut microbiota

Abstract

The complex human colonic microbiota plays a key role in gut health, and both the composition and metabolism of the gut microbiota are strongly diet related. Controlled dietary intake studies in obese individuals demonstrated that consumption of low-carbohydrate diets results in low faecal butyrate concentrations together with a low abundance of the major butyrate-producing bacteria, Roseburia spp. and Eubacterium rectale group.Resistant dietary carbohydrates, including pre-biotics, escape digestion in the upper gastrointestinal tract and are fermented to short-chain fatty acids (SCFAs) by bacteria in the colon. The main SCFAs formed are acetate, propionate and butyrate. Model colonic fermentor systems employed to determine which bacterial groups utilise specific substrates indicated that the bacterial composition and production of SCFAs is substrate dependent. The bacterial colonisers of specific substrates were identified using 16S rRNA sequence analysis. Sequences recovered from bran were most closely related to Roseburia spp., E. rectale and Clostridium hathewayi, while on resistant starch, sequences were most closely related to Ruminococcus bromii and Bifidobacterium adolescentis.Differing intakes of dietary carbohydrate also impact on other factors in the colon such as transit and pH. In continuous fermentor systems, a slightly acidic pH (5.5) representative of the proximal colon gave fourfold higher butyrate concentrations than at the higher pH of 6.5, which is more representative of the distal colon. Bacteroidetes dominated the fermentor at pH 6.5, while the major butyrateproducing bacterial groups competed more effectively for carbohydrate substrates when the pH was mildly acidic (5.5). In in vitro studies in which pH values were even lower, pH 5.2, lactate and acetate accumulated. In contrast, lactate was not detected at pH 6.4 although stable isotope studies revealed that lactate was actively produced. Lactate accumulation at low pH appears to be as a result of the loss of lactate-utilising bacteria including Eubacterium hallii.It is clear that the composition of the colonic microbiota and the balance of its metabolic products is strongly influenced by diet and, in particular, by the intake of resistant carbohydrates and dietary fibre.

Functionality and Application of Dietary Fiber in Meat Products

“…Also, butyrate is the preferred sources for the growth and differentiation of colonic cells and possibly inhibits tumor growth (McIntyre et al, 1993). The formation of SCFA decreases the pH in the gut and thereby inhibits the growth of harmful bacteria while aiding the growth of bifidobacteria and lactic acid microflora (Scott et al, 2008).…”

The art of targeting gut microbiota for tackling human obesity

“…The so-called Western diet is characterized by an unbalanced high content of refined carbohydrates when compared to other diets from the early human history, or those typical for developing countries (Scott et al 2008). The potential of prebiotics to reduce food intake, fat mass development and body weight was demonstrated more than 10 years ago by changing the gut microbiota (with prebiotics such as inulin and oligofructose) and the cross-talk between the brain and gut microbiota (Cani et al 2004Delzenne et al 2005).…”

Evaluation of rheological, bioactives and baking characteristics of mango ginger (curcuma amada) enriched soup sticks

“…Since the endogenous fiber polysaccharide content in wheat flour is only 4 %, the incorporation of dietary fiber in wheat flour based product such as bread would raise the health profile of the final products (Scott et al 2008). There are many scientific reports on the therapeutic properties of mango ginger and their potential pharmaceutical applications.…”